Combine cola beverage, white sugar, soy sauce, water, green onions, sesame oil, garlic, sesame seeds, and black pepper in a bowl until marinade is well-mixed.
Place short ribs in a resealable plastic bag and pour in marinade. Squeeze out excess air and seal the bag. Marinate in the refrigerator for at least 2 hours.
Preheat an outdoor grill for medium-high heat and lightly oil the grate. Remove short ribs from marinade, discarding marinade.
Cook short ribs until browned and cooked to desired doneness, 3 to 4 minutes per side. An instant-read thermometer inserted into the center should read 145 degrees F (63 degrees C).
